In recent years, amongst methods for forming microscopic structures and microscopic components typified by MEMS (Micro ElectroMechanical Systems), formation methods that use a combination of a thick-film lithography method and a plating method are attracting much attention.
However, with conventional methods, the formation of thick films is problematic, and the fabrication of high-precision three dimensional shapes in which the shape varies through the thickness direction, such as the formation of gears of differing diameter, has proven particularly difficult.
Examples of such formation methods include a method of processing a photoresist disclosed in a patent reference 1, wherein a complex exposure operation using different mask patterns and different exposure doses, and including overlapping exposure regions, is performed on a photoresist layer, and the photoresist layer is then developed, forming stepped concave sections within the photoresist layer.
Furthermore, a patent reference 2 discloses a method of forming an opening within a substrate, comprising a step of forming a first layer of a positive photoresist on the substrate, a step of exposing the first layer with a quantity of photochemically active radiation that is sufficient to partially decompose an activator in the positive photoresist but insufficient to cause dissolution in the developing solution, a step of applying a second layer of a positive photoresist on top of the first layer, a step of performing pattern exposure of the first and second layers with a sufficient quantity of photochemically active radiation to cause dissolution of both the first and second positive photoresists within the developing solution, and a step of developing the first and second layers to form an opening through the first and second layers.
[Patent Reference 1]
Japanese Unexamined Patent Application, First Publication No. 2003-29415
[Patent Reference 2]
Japanese Unexamined Patent Application, First Publication No. Hei 9-199663